The invention relates to an electrical shutter circuit for camera which provides an automatic, proper control of the shutter open time in accordance with the brightness of an object being photographed.
As is well known, a camera incorporating an electrical shutter is constructed such that the depression of a shutter button is effective to operate a shutter assembly for an opening movement so as to open an exposure light path to initiate an exposure operation, and simultaneously a photoelectric transducer element contained within an electrical shutter control circuit becomes responsive to reflected light from an object being photographed so that when a proper exposure period has elapsed, the electrical shutter control circuit operates to close the shutter assembly automatically. However, with a camera of this kind, there is a disadvantage that a shutter assembly, once released, remains open for an indenfinite period of time where reflective light from an object being photographed is absent or extremely weak. For example, when the shutter is operated with a camera directed toward the darkness or when the shutter is inadvertently released when encasing the camera, the shutter remains open. The exposure period for the shutter will be from several minutes to an indefinite period of time in this instance, so that the battery will be exhausted in vain, preventing subsequent photographing operations.
The above disadvantage is also involved when loading film into the camera in a dim place. Specifically, when loading film into the camera, it is initially necessary to provide an idle film feed for the first two or three frames. With a camera of a self-cocking type, the film winding operation is prevented unless the exposure through the shutter is completed. Because an incident light directed onto an electrical shutter is reduced in a dim place, an automatic completion of the shutter operation is prevented, thus precluding an idle film feeding operation.